Power is generally transmitted between a V transmission belt and a pulley through sliding friction. The greater the frictional force, the higher the transmission power. When a frictional force is large, a slippage between the V belt and the pulley becomes less likely. Currently, a V-pulley is formed by casting, and then annealing. Finally, precise machining is performed on the surface of the V-pulley. A V-pulley made by such a method has a desirable smooth side V belt grooves surfaces. However, such a smooth surface has a low friction coefficient, therefore, the transmission power is limited. When high power transmission is desirable, slippage may easily occur between a V belt and a pulley.
Chinese Patent Publication No. CN102218509A discloses a casting mold for a V belt pulley having belt grooves. A pulley is integrally formed by casting, and then subsequent thermal treatment and precise machining are performed to form a pulley. The side surfaces of belt grooves of the pulley have desirable smoothness, but a low friction coefficient. Therefore transmission power is relatively low, and such a belt is likely to slip. Chinese Patent Publication No. CN1301202A discloses a method of manufacturing a multi-V-groove belt pulley. Multiple V grooves are formed into a two-level multi-V-groove belt pulley. In a belt pulley manufactured by this method, the side surfaces of belt grooves have a relatively low friction coefficient, and therefore transmission power is also relatively low and a belt is likely to slip.